We propose a mathematical model of multiple interference phenomena occurring inside the dielectric cavity of the metasurface absorber. Subsequently, it derived the expressions for electric and magnetic fields within the structure. The model enables one to mathematically interpret wave propagation, standing wave formation, and absorption in terms of electric and magnetic fields. We also discussed the effect of change in the polarization angle of the incident electromagnetic wave on the standing wave pattern and surface-current orientation. The study reveals that the theory is equally applicable for transverse electric and transverse magnetic polarized incident waves. All the mathematical aspects of the theory have been analytically established through the validation of simulation data. It has been found that the theory is in good agreement with the analytically obtained results.
A wrinkle-network structure of Mn doped ZnO is presented in this paper. The undoped and Mn doped ZnO thin film samples have been prepared on ITO coated glass substrates by sol-gel spin coating technique as it is a simple and lowcost method to deposit semiconductor thin films. High resolution X-ray diffraction technique confirms the formation of hexagonal wurtzite structure with diffraction pattern corresponding to ZnO. Mn related phases have not been observed within the detection limit of HR-XRD. The incorporation of Mn dopant in the sample has been confirmed by energy dispersive X-ray spectroscopy (EDS). Both the undoped and Mn doped samples have high optical transmittance in the wavelength range of 300 nm – 800 nm, with a maximum of 88% as recorded by UV-VIS spectroscopy. There is an increase in the bandgap of ZnO thin films by the introduction of Mn dopants which has been calculated by Tauc plot.
We report on characterization of Pd/ZnO nanostructure thin film Schottky contacts based UV photodetector. The ZnO film was grown on p-type Si ‹100› substrate by using vacuum thermal evaporation method. With applied voltage in the range from -2V to 2V we estimated the photocurrent, contrast-ratio, responsivity and quantum-efficiency of the photodetectors for an incident optical power of 0.1mW at 365nm ultraviolet wavelength. The I-V characteristics were studied and the parameters such as ideality-factor, leakage-current, and barrier-height of the Schottky contacts were extracted from the measured data. The surface morphological and the structural properties of the thin film were studied by atomic force microscope (AFM) and scanning electron microscopy (SEM). The bandgap of ZnO is evaluated from the absorbance spectra of ZnO thin film obtained by using double beam spectrophotometer. For the investigation of the surface chemical bonding, X-ray photoelectron spectroscopy (XPS) measurements were also performed. The device exhibited good stability, high efficiency and high sensitivity under the reverse bias condition. For forward bias, the UV detection sensitivity decreased proportionally to the bias voltage.
Fabrication and electrical characterization of a Pd/TiO2/n-Si MIS structure have been reported in this paper. The TiO2 layer has been deposited on n-Si by using low temperature arc vapor deposition (LTAVD) technique. The currentvoltage and capacitance-voltage characteristics were studied at room temperature (300 K) for sample devices with TiO2 film annealed at different temperatures (450 to 550°C). The study reveals that the capacitance in the accumulation region has frequency dispersion at high frequencies which is attributed to leakage behavior of TiO2 insulating layer, interface states and oxide defects. As-deposited film exhibits high level of interface states resulting in high leakage current density which can be reduced by an order of magnitude by post-deposition annealing. Different models of current conduction mechanism have been applied to study the measured data. It is found that Schottky–Richardson (SR) emission model is applicable at low bias voltage, Frenkel-Poole (FP) emission model at moderate bias voltages while Fowler–Nordheim (FN) tunneling dominates at higher bias voltages.
A ZnO based thin film transistor (TFT) with bottom-gate configuration and SiO2 as insulating layer has been fabricated
and characterized. The ZnO thin film was prepared by spin coating the sol-gel solution on the p-type Si wafers. The
optical and structural properties of ZnO films were investigated using UV measurements and scanning electron
microscope (SEM). The result of UV-visible study confirms that the films have a good absorbance in UV region and
relatively low absorbance in the visible region. The TFT exhibited an off-current of 2.5×10-7 A. The values of field effect
channel mobility and on/off current ratio extracted for the device, measured 11 cm2/V.s and ~102 respectively. The value
of threshold voltage was found to be 1.3 V.
The fabrication and characterization of heterojunction phtodiodes for room temperature operation in the mid-infrared (2-5 μm) spectral range is described. Liquid phase epitaxy was employed to fabricate two different devices containing In0.97Ga0.03As and InAs0.89Sb0.11 active regions appropriate for phtodetection at 3.3 μm and 4.6 μm, corresponding to the absorption bands of methane and carbon monoxide. Basic detector characteristics have been measured and were found to compare favourbly with other available detectors in this wavelength range. A simple analystical model was developed to help design and study the corresponding device physics governing the performance of the detectors and was found to give good agreement with the experimentally measured values.
We present the design and analysis of an optical receiver front-end configuration that uses a single heterojunction bipolar transistor for both photodetection and amplification purpose. The performance characteristics an InP/InGaAs HBT receiver operating in 1.55 μm wavelength region have been studied on the basis of our model. Theoretical results indicate a high transimpedance gain (~54 dBΩ), a large bandwidth (~29.5 GHz) and a reasonably high sensitivity (-24 dBm at 10 Gb/s) for the receiver configuration. Use of a single HBT in the front-end would greatly simplify the fabrication of optoelectronic integrated circuit (OEIC) receiver in the monolithic form.
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